shortening before rendering on the fusion

I spent an hour and a half rolling and the Fusion recorded no problem, but now my computer times out before even the low res preview can be rendered by Fusion Studio. When I look at the files I can see that they are manageable sized chunks (there's 13 Front and 13 back MP4s). Can I stitch these smaller files individually rather than just rendering a full size 1.5 hour file?